More than 2000 years ago Hippocrates (460-377 BCE) said, "If we could give every individual the right amount of nourishment and exercise, not too little and not too much, we would have found the safest way to health." What does that mean when it comes to water? Water has been described as a neglected, unappreciated, and under-researched subject, and further complicating the issue, a lot of the papers extolling the need for proper hydration are funded by the bottled water industry.

It turns out the often quoted "drink at least eight glasses of water a day" dictum has little underpinning scientific evidence . Where did that idea come from? The recommendation was traced to a 1921 paper, in which the author measured his own pee and sweat and determined we lose about 3% of our body weight in water a day, or about 8 cups (see How Many Glasses of Water Should We Drink in a Day?). Consequently, for the longest time, water requirement guidelines for humanity were based on just one person.

There is evidence that not drinking enough may be associated with falls and fractures, heat stroke, heart disease, lung disorders, kidney disease, kidney stones, bladder and colon cancer, urinary tract infections, constipation, dry mouth, cavities, decreased immune function and cataract formation. The problem with many of these studies is that low water intake is associated with several unhealthy behaviors, such as low fruit and vegetable intake, more fast-food, less shopping at farmers markets. And who drinks lots of water? People who exercise a lot. No wonder they tend to have lower disease rates!

Only large and expensive randomized trials could settle these questions definitively. Given that water cannot be patented, such trials seem unlikely; who's going to pay for them? We're left with studies that find an association between disease and low water intake. But are people sick because they drink less, or are they drinking less because they're sick? There have been a few large prospective studies in which fluid intake is measured before disease develops. For example, a Harvard study of 48,000 men found that the risk of bladder cancer decreased by 7% for every extra daily cup of fluid we drink. Therefore, a high intake of water--like 8 cups a day--may reduce the risk of bladder cancer by about 50%, potentially saving thousands of lives.

The accompanying editorial commented that strategies to prevent the most prevalent cancers in the West are remarkably straightforward in principle. To prevent lung cancer, quit smoking; to prevent breast cancer, maintain your ideal body weight and exercise; and to prevent skin cancer, stay out of the sun. Now comes this seemingly simple way to reduce the risk of bladder cancer: drink more fluids.

Probably the best evidence we have for a cut off of water intake comes from the Adventist Health Study, in which 20,000 men and women were studied. About one-half were vegetarian, so they were also getting extra water by eating more fruits and vegetables. Those drinking 5 or more glasses of water a day had about half the risk of dying from heart disease compared to those who drank 2 or fewer glasses a day. Like the Harvard study, this protection was found after controlling for other factors such as diet and exercise. These data suggest that it was the water itself that was decreasing risk, perhaps by lowering blood viscosity (blood thickness).

Based on all the best evidence to date, authorities from Europe, the U.S. Institute of Medicine, and the World Health Organization recommend between 2.0 and 2.7 liters (8 to 11 cups) of water a day for women, and 2.5 to 3.7 liters (10 to 15 cups) a day for men. This includes water from all sources, not just beverages. We get about a liter from food and the water our body makes. So this translates into a recommendation for women to drink 4 to 7 cups of water a day and men 6 to 11 cups, assuming only moderate physical activity at moderate ambient temperatures.

We can also get water from all the other drinks we consume, including caffeinated drinks, with the exception of stronger alcoholic drinks like wines and spirits. Beer can leave you with more water than you started with, but wine actively dehydrates you. However, in the cancer and heart disease studies I mentioned above, the benefits were only found with increased water consumption, not other beverages.

Surprised that the 8-a-day rested on such flimsy evidence? Unfortunately, so much of what we do in medicine has shaky underpinnings. That's the impetus behind the idea of evidence-based medicine (what a concept!). Ironically, this new movement may itself undermine some of the most effective treatments. See Evidence-Based Medicine or Evidence-Biased?

What kind of water? I recommend tap water, which tends to be preferable from a chemical and microbial contamination standpoint. What about buying one of those fancy alkalizing machines? See Alkaline Water: a Scam?

More than 2000 years ago Hippocrates (460-377 BCE) said, "If we could give every individual the right amount of nourishment and exercise, not too little and not too much, we would have found the safest way to health." What does that mean when it comes to water? Water has been described as a neglected, unappreciated, and under-researched subject, and further complicating the issue, a lot of the papers extolling the need for proper hydration are funded by the bottled water industry.

It turns out the often quoted "drink at least eight glasses of water a day" dictum has little underpinning scientific evidence . Where did that idea come from? The recommendation was traced to a 1921 paper, in which the author measured his own pee and sweat and determined we lose about 3% of our body weight in water a day, or about 8 cups (see How Many Glasses of Water Should We Drink in a Day?). Consequently, for the longest time, water requirement guidelines for humanity were based on just one person.

There is evidence that not drinking enough may be associated with falls and fractures, heat stroke, heart disease, lung disorders, kidney disease, kidney stones, bladder and colon cancer, urinary tract infections, constipation, dry mouth, cavities, decreased immune function and cataract formation. The problem with many of these studies is that low water intake is associated with several unhealthy behaviors, such as low fruit and vegetable intake, more fast-food, less shopping at farmers markets. And who drinks lots of water? People who exercise a lot. No wonder they tend to have lower disease rates!

Only large and expensive randomized trials could settle these questions definitively. Given that water cannot be patented, such trials seem unlikely; who's going to pay for them? We're left with studies that find an association between disease and low water intake. But are people sick because they drink less, or are they drinking less because they're sick? There have been a few large prospective studies in which fluid intake is measured before disease develops. For example, a Harvard study of 48,000 men found that the risk of bladder cancer decreased by 7% for every extra daily cup of fluid we drink. Therefore, a high intake of water--like 8 cups a day--may reduce the risk of bladder cancer by about 50%, potentially saving thousands of lives.

The accompanying editorial commented that strategies to prevent the most prevalent cancers in the West are remarkably straightforward in principle. To prevent lung cancer, quit smoking; to prevent breast cancer, maintain your ideal body weight and exercise; and to prevent skin cancer, stay out of the sun. Now comes this seemingly simple way to reduce the risk of bladder cancer: drink more fluids.

Probably the best evidence we have for a cut off of water intake comes from the Adventist Health Study, in which 20,000 men and women were studied. About one-half were vegetarian, so they were also getting extra water by eating more fruits and vegetables. Those drinking 5 or more glasses of water a day had about half the risk of dying from heart disease compared to those who drank 2 or fewer glasses a day. Like the Harvard study, this protection was found after controlling for other factors such as diet and exercise. These data suggest that it was the water itself that was decreasing risk, perhaps by lowering blood viscosity (blood thickness).

Based on all the best evidence to date, authorities from Europe, the U.S. Institute of Medicine, and the World Health Organization recommend between 2.0 and 2.7 liters (8 to 11 cups) of water a day for women, and 2.5 to 3.7 liters (10 to 15 cups) a day for men. This includes water from all sources, not just beverages. We get about a liter from food and the water our body makes. So this translates into a recommendation for women to drink 4 to 7 cups of water a day and men 6 to 11 cups, assuming only moderate physical activity at moderate ambient temperatures.

We can also get water from all the other drinks we consume, including caffeinated drinks, with the exception of stronger alcoholic drinks like wines and spirits. Beer can leave you with more water than you started with, but wine actively dehydrates you. However, in the cancer and heart disease studies I mentioned above, the benefits were only found with increased water consumption, not other beverages.

Surprised that the 8-a-day rested on such flimsy evidence? Unfortunately, so much of what we do in medicine has shaky underpinnings. That's the impetus behind the idea of evidence-based medicine (what a concept!). Ironically, this new movement may itself undermine some of the most effective treatments. See Evidence-Based Medicine or Evidence-Biased?

What kind of water? I recommend tap water, which tends to be preferable from a chemical and microbial contamination standpoint. What about buying one of those fancy alkalizing machines? See Alkaline Water: a Scam?

Ever since smoking was prohibited in night clubs, customers have increasingly noticed other unpleasant smells present in the club--like body odors. So, researchers in Europe thought they'd try to cover them up. The researchers measured the effects of peppermint, for example, on dancing activity and asked people to rate their energy level. They found that with peppermint scent, people felt more cheerful and danced more, and so, concluded the researchers, "environmental fragrancing may be expected to have a positive effects on club revenue." Innovative nightclubs are already inviting "aroma jockeys" to smell the places up.

The business community caught whiff of this and thought maybe peppermint smell would get their secretaries to type faster. And it worked! There was improved performance on clerical tasks associated with the administration of peppermint odor.

In an age where athletic competitions are frequently won or lost by mere hundredths of a second, athletes are continually looking for new ways to excel in their sport. Researchers threw some collegiate athletes onto a treadmill and piped different smell into their nostrils, and those on peppermint reported feeling less fatigued, more vigorous, less frustrated, and felt they performed better. But did they actually perform better? See my video, Enhancing Athletic Performance with Peppermint.

A different study published in the Journal of Sport and Exercise Psychology measured actual performance, and participants were actually able to squeeze out one extra pushup before collapsing and cut almost two seconds off a quarter mile dash with an odorized adhesive strip stuck to their upper lip. Interestingly there was no significant difference in basketball free throws. The researchers think the reason is that free throws actually require some skill, and all the peppermint can do is really improve athlete's motivation.

Unfortunately follow-up studies were not able to replicate these results, showing no beneficial effect of smelling peppermint on athletic performance, so how about eating peppermint? Researchers measured the effects of peppermint on exercise performance before and after ten days of having subjects drink bottles of water with a single drop of peppermint essential oil in them. And all the subjects' performance parameters shot up, churning out 50 percent more work, 20 percent more power, and a 25 percent greater time to exhaustion. Improvements were found across the board in all those physiological parameters, indicating increased respiratory efficiency. They attribute these remarkable results to the peppermint opening up their airways, increasing ventilation and oxygen delivery.

Now, you can overdose on the stuff, but a few drops shouldn't be toxic. Why not get the best of both worls by blending fresh mint leaves in water rather than use the oil?

A number of case-control studies have found that giving kids cod liver oil supplements may increase their risk of asthma later in life. Case-control studies are done by asking about past behavior in cases (those with asthma) versus controls (those without asthma) to see if certain past behaviors are more likely among the disease group. The problem is that asking people to remember what they were doing years ago, when most people can't remember what they had for breakfast last week, is unreliable. When interpreting the results from case-control studies, we also can't rule out something called reverse causation. Maybe cod liver oil doesn't lead to asthma, but asthma led to the use of cod liver oil.

It would therefore be nice to see a cohort study. In a cohort study, researchers would take people without asthma and follow them over time to see if those taking cod liver oil are more likely to develop it. Because people without the disease and their diets are followed over time, cohort studies bypass the problems of recall bias and reverse causation.

In 2013, we finally got one such study. 17,000 people free of asthma were followed over 11 years. Researchers knew who was taking cod liver oil and who wasn't, and then sat back and watched to see who got asthma over the subsequent 11 years. The researchers found that cod liver oil intake was indeed significantly associated with the development of asthma. They thought it might be the excessive vitamin A in the cod liver oil that was causing the problem, but there are also a number of substances in fish oil we may not want our children exposed to.

Researchers from Philadelphia University, highlighted in my video PCBs in Children's Fish Oil Supplements, recently looked at 13 over-the-counter children's dietary supplements containing fish oil to assess potential exposure to PCBs, toxic industrial pollutants that have contaminated our oceans. PCBs were detected in all products. Could we just stick to the supplements made from small, short-lived fish like anchovies instead of big predator fish like tuna to reduce the impact of biomagnification? Or use purified fish oils? No, the researchers found no significant difference in PCB levels whether the supplements were labeled as molecularly distilled or how high up the food chain the fish were.

The researchers concluded that while children's dietary supplements containing the long-chain omega-3's from fish oils may claim to benefit young consumers, "daily ingestion of these products may provide a vector for contaminant exposure that may off-set the positive health effects." What positive health benefits are they talking about?

Researchers publishing in the journal, Early Human Development, found that infants given DHA-fortified formula may have better development of their eyes and brains compared to infants getting non DHA-fortified formula. What was the source of the DHA? Not fish, but algae-derived DHA. In that way we can get the benefits of omega 3's without the contaminant risks. But of course, breast milk is the gold standard, significantly better than either of the formula fed infants. So the best source of omega-3's is mom.

It's bad enough when supplement manufacturers exploit adults when they're sick and vulnerable with pills that are often useless or worse, but taking advantage of our parental drive to do what's best for our children with contaminated products that may make them sick, makes me sick.

Dr. Esselstyn's landmark study, demonstrating that even advanced triple vessel coronary artery disease could be reversed with a plant-based diet, has been criticized for being such a small study. But the reason we're used to seeing large studies is that they typically show such small effects. Drug manufacturers may need to study 7,000 people in order to show a barely statistically significant 15% drop in ischemic events in a subsample of patients. Esselstyn achieved a 100% drop in those who stuck to his diet, all the more compelling considering that those 18 participants experienced 49 coronary events (like heart attacks) in the eight years before they went on the diet. These patients were the sickest of the sick, most of whom having already failed surgical intervention. When the effects are so dramatic, how many people do you need?

Before 1885, a symptomatic rabies infection was a death sentence, until little Joseph Meister became the first to receive Pasteur's experimental rabies vaccine. The results of this and one other case were so dramatic compared with previous experience that the new treatment was accepted with a sample size of two. That is, the results were so compelling that no randomized controlled trial was necessary. Having been infected by a rabid dog, would you be willing to participate in a randomized controlled trial, when being in the control group had a certainty of a ''most awful death''? Sadly, such a question is not entirely rhetorical.

In the 1970's, a revolutionary treatment for babies with immature lungs called "extracorporeal membranous oxygenation" (ECMO), transformed immature lung mortality from 80% dead to 80% alive nearly overnight. The standard therapy caused damage to infants' lungs and was a major cause of morbidity and mortality in infants. ECMO is much gentler on babies' lungs, "providing life support while allowing the lungs to 'rest.'"

Despite their dramatic success, the researchers who developed ECMO felt forced to perform a randomized controlled trial. They didn't want to; they knew they'd be condemning babies to death. They felt compelled to perform such a trial because their claim that ECMO worked would, they judged, carry little weight amongst their medical colleagues unless supported by a randomized controlled trial. Therefore, at Harvard's Children's Hospital, 39 infants were randomized to either get ECMO or conventional medical therapy. The researchers decided ahead of time to stop the trial after the 4th death so as not to kill too many babies. And that's what they did. The study was halted after the fourth conventional medical therapy death, at which point nine out of nine ECMO babies had survived. Imagine being the parent to one of those four children.

Similarly, imagine being the child of a parent who died other conventional medical or surgical therapy for heart disease.

In her paper "How evidence-based medicine biases physicians against nutrition," Laurie Endicott Thomas reminds us that medical students in the United States are taught very little about nutrition (See Evidence-Based Medicine or Evidence-Biased?). Worse yet, according to Thomas, their training actually biases them against the studies that show the power of dietary approaches to managing disease by encouraging them to ignore any information that does not come from a double-blind, randomized controlled trial. Yet humans cannot be blinded to a dietary intervention--we tend to notice what we're eating--and, as a result, physicians are biased in favor of drug treatments and against dietary interventions for the management of chronic disease.

Evidence-based medicine is a good thing. However, Thomas points out that the medical profession may be focusing too much on one type of evidence to the exclusion of all others. Unfortunately, this approach can easily degenerate into "ignoring-most-of-the-truly-important-evidence" based medicine.

Heart disease is a perfect example. On healthy enough plant based diets, our number one cause of death may simply cease to exist. The Cornell-Oxford-China Study showed that even small amounts of animal-based food was associated with a small, but measurable increase in the risk of some chronic diseases. In other words, "the causal relationship between dietary patterns and coronary artery disease was already well established before Dean Ornish and Caldwell Esselstyn undertook their clinical studies." The value of their studies was not so much in providing evidence that such a dietary change would be effective, but in showing that "physicians can persuade their patients to make such changes," and in "providing interesting data on the speed and magnitude of the change in severe atherosclerotic lesions as a result of dietary therapy."

Therefore, any complaints that these studies were small or unblinded are simply irrelevant. Because the evidence of the role of diet in causing atherosclerosis is already so overwhelming, "assigning a patient to a control group eating the standard American diet could be considered a violation of research ethics."

Evidence of the value of plant-based diets for managing chronic disease has been available in the medical literature for decades. Walter Kempner at Duke University, John McDougall, the Physician's Committee for Responsible Medicine, Nathan Pritikin, and Denis Burkitt all warned us that the standard Western diet is the standard cause of death and disability in the Western world. Yet physicians, especially in the US, are still busily manning the ambulances at the bottom of the cliff instead of building fences at the top.

I previously discussed the power of fruits and vegetables to help prevent and treat asthma and allergies. If adding a few more servings of fruits and vegetables may help asthma, what about a diet centered around plants? Twenty patients with allergic eczema were placed on a vegetarian diet. At the end of two months, their disease scores, which covered both subjective and objective signs and symptoms, were cut in half, similar to what we might see using one of our most powerful drugs. The drug works much quicker, within about two weeks, but since drugs can often include dangerous side effects the dietary option is more attractive. This was no ordinary vegetarian diet, however. This was an in-patient study using an extremely calorically-restricted diet--the subjects were practically half fasting. Therefore, we don't know which component was responsible for the therapeutic effect.

What about using a more conventional plant-based diet against a different allergic disease, asthma? In Sweden, there was an active health movement that claimed that a vegan diet could improve or cure asthma. This was a bold claim, so in order to test this, a group of orthopedic surgeons at Linköping University Hospital followed a series of patients who were treated with a vegan regimen for one year. (This study is highlighted in my video, Treating Asthma and Eczema with Plant-Based Diets.) Participants had to be willing to go completely plant-based, and they had to have physician-verified asthma of at least a year's duration that wasn't getting better or was getting worse despite the best medical therapies available.

The researchers found quite a sick group to follow. The thirty-five patients had long-established, hospital-verified bronchial asthma for an average duration of a dozen years. Of the 35 patients, 20 had been admitted to the hospital for acute asthmatic attacks during the last two years. Of these, one patient had received acute infusion therapy (emergency IV drugs) a total of 23 times during this period and another patient claimed he had been to the hospital 100 times during his disease and on every occasion had evidently required such treatments. One patient even had a cardiac arrest during an asthma attack and had been brought back to life on a ventilator. These were some pretty serious cases.

The patients were on up to eight different asthma medicines when they started, with an average of four and a half drugs, and were still not getting better. Twenty of the 35 were constantly using cortisone, which is a powerful steroid used in serious cases. These were all fairly advanced cases of the disease, more severe than the vegan practitioners were used to.

Eleven couldn't stick to the diet for a year, but of the 24 that did, 71% reported improvement at four months and 92% at one year. These were folks that had not improved at all over the previous year. Concurrently with this improvement, the patients greatly reduced their consumption of medicine. Four had completely given up their medication altogether, and only two weren't able to at least drop their dose. They went from an average of 4.5 drugs down to 1.2, and some were able to get off cortisone.

Some subjects said that their improvement was so considerable they felt like "they had a new life." One nurse had difficulty at work because most of her co-workers were smokers, but after the plant-based regimen she could withstand the secondhand smoke without getting an attack and could tolerate other asthma triggers. Others reported the same thing. Whereas previously they could only live in a clean environment and felt more or less isolated in their homes, they could now go out without getting asthmatic attacks.

The researchers didn't find only subjective improvements. They also found a significant improvement in a number of clinical variables, most importantly in measures of lung function, vital capacity, forced expiratory volume, and physical working capacity, as well as significant drops in sed rate (a marker of inflammation) and IgE (allergy associated antibodies).

The study started out with 35 patients who had suffered from serious asthma for an average of 12 years, all receiving long-term medication, with 20 using cortisone, who were "subjected to vegan food for a year," and, in almost all cases, medication was withdrawn or reduced, and asthma symptoms were significantly reduced.

Despite the improved lung function tests and lab values, the placebo effect can't be discounted since there was no blinded control group. However, the nice thing about a healthy diet is that there are only good side effects. The subjects' cholesterol significantly improved, their blood pressures got better, and they lost 18 pounds. From a medical standpoint, I say why not give it a try?

If you missed the first three videos of this 4-part series here are the links:

In my video Treating Asthma With Fruits and Vegetables, I highlighted a landmark study on manipulating antioxidant intake in asthma. The study found that just a few extra fruits and vegetables a day can powerfully reduce asthma exacerbation rates. If the antioxidants in the plants are ameliorating asthma, then why can't we take antioxidant pills instead? Because antioxidant pills don't appear to work.

Studies using antioxidant supplements on respiratory or allergic diseases have mostly shown no beneficial effects. This discrepancy between data relating to fruit and vegetable intake compared with those using antioxidant supplements may indicate the importance of the whole food, rather than individual components. For example, in the Harvard Nurse's Health Study, women who got the most vitamin E from their diet appeared to be at half the risk for asthma, (which may help explain why nut consumption is associated with significantly lower rates of wheezing), but vitamin E supplements did not appear to help.

Men who eat a lot of apples appear to have superior lung function, as do kids who eat fresh fruit every day, as measured by FEV1 (basically how much air you can forcibly blow out in one second). The more fruit, salad, and green vegetables kids ate, the greater their lung function appeared.

Researchers are "cautious about concluding which nutrient might be responsible." There's vitamin C in fruits, salads, and green vegetables, but there are lots of other antioxidants, such as "vitamin P," a term used to describe polyphenol phytonutrients found in grapes, flax seeds, beans, berries, broccoli, apples, citrus, herbs, tea, and soy. Polyphenol phytonutrients can directly bind to allergenic proteins and render them hypoallergenic, allowing them to slip under our body's radar. If this first line of defense fails, polyphenols can also inhibit the activation of the allergic response and prevent the ensuing inflammation, and so may not only work for prevention, but for treatment as well.

Most of the available evidence is weak, though, in terms of using supplements containing isolated phytonutrients to treat allergic diseases. We could just give people fruits and vegetables to eat, but then we couldn't perform a double-blind study to see if they work better than placebo. Some researchers decided to use pills containing plant food extracts. Plant extracts are kind of a middle ground. They are better than isolated plant chemicals, but are not as complete as whole foods. Still, since we can put whole foods in a capsule, we can compare the extracts to fake sugar pills that look and feel the same to see if they have an effect.

The first trial involved giving people extracts of apple skins. I've talked about the Japan's big cedar allergy problem before (See Alkylphenol Endocrine Disruptors and Allergies), so apple extract pills were given every day for a few months starting right before pollen season started. The results were pretty disappointing. They found maybe a little less sneezing, but the extract didn't seem to help their stuffy noses or itchy eyes.

What about a tomato extract? A randomized, double-blind, placebo-controlled eight-week trial was performed on perennial allergic rhinitis, this time not for seasonal pollen, but for year-round allergies to things like dust-mites. There are lots of drugs out there, but you may have to take them every day year-round, so how about some tomato pills instead? After oral administration of tomato extract for eight weeks, there was a significant improvement of total nasal symptom scores, combined sneezing, runny nose and nasal obstruction, with no apparent adverse effects.

Would whole tomatoes work even better? If only researchers would design an experiment directly comparing phytonutrient supplements to actual fruits and vegetables head-to-head against asthma, but such a study had never been done... until now. The same amazing study, highlighted in my video, Treating Asthma with Plants vs. Supplements?, that compared the seven-fruit-and-vegetables-a-day diet to the three-fruit-and-vegetables-a-day diet, after completion of its first phase, commenced a parallel, randomized, controlled supplementation trial with capsules of tomato extract, which boosted the power of five tomatoes in one little pill, and the study subjects were given three pills a day.

Who did better, the group that ate seven servings of actual fruits and vegetables a day, or the group that ate three servings a day but also took 15 supposed serving equivalents in pill form? The pills didn't help at all. Improvements in lung function and asthma control were evident only after increased fruit and vegetable intake, which suggests that whole-food interventions are most effective. Both the supplements and increased fruit and vegetable intake were effective methods for increasing carotenoid concentrations in the bloodstream, but who cares? Clinical improvements--getting better from disease--were evident only as a result of an increase in plant, not pill, consumption. The results provide further evidence that whole-food approaches should be used to achieve maximum efficacy of antioxidant interventions.

In my video Preventing Asthma With Fruits and Vegetables, I highlighted an international study of asthma and allergies involving more than a million kids. The study found a consistent inverse relationship between prevalence rates of asthma, allergies, and eczema and the intake of plants, starch, grains, and vegetables. Researchers speculated "over a decade ago that if these findings could be generalized, and if the average daily consumption of these foods increased, an important decrease in symptom prevalence could be achieved." No need to speculate any more, though, because plants were finally put to the test.

Researchers have proposed that "by eating fewer fruits and vegetables, the susceptibility to potentially harmful inhaled substances of the population as a whole may be increased because of the reduction in antioxidant defenses of the lungs." The thin lining of fluid that forms the interface between our respiratory tract and the external environment is our first line of defense against oxidative damage. Oxidative damage is important in asthma, contributing to airway contraction, excessive mucous production, and hypersensitivity. Antioxidants protect against oxidative stress, so our lung lining contains a range of antioxidants our body makes itself, as well as those obtained from our diet, particularly from fruits and vegetables.

We can even quantify the level of oxidative stress in people by measuring the level of oxidation products in their exhaled breath, which drops as we start eating more fruits and vegetables, and drops further as we combine more plants with fewer animal foods.

Do those with asthma really have lower levels of antioxidants than people without asthma? Compared to healthy controls, subjects with asthma had lower whole blood levels of total carotenoids and lower levels of each of the individual phytonutrients they measured: cryptoxanthin, lycopene, lutein, alpha-carotene and beta-carotene compared to healthy controls.

Therefore, they posit, "the accumulating evidence does suggest that diet has an influence in modulating the response of the lung to inhaled allergens and irritants. However, it is possible that the reduced carotenoid levels in asthma are a result of increased utilization in the presence of excess free radicals." So it's like a chicken-or-the-egg phenomenon.

We know antioxidant-rich diets have been associated with reduced asthma prevalence. However, direct evidence that altering intake of antioxidant-rich foods actually affects asthma was lacking, until now.

There are two ways to test the effects of fruits and vegetables on asthma. Add fruits and vegetables to people's diets and see if their asthma improves, or take asthmatics and remove fruits and vegetables from their diets and see if they get worse.

The first such study of its kind, highlighted in my video, Treating Asthma With Fruits and Vegetables, placed subjects with asthma on a low antioxidant diet. After just a matter of days, there was a significant worsening of lung function and asthma control. The researchers conclude that "This finding is highly significant for subjects with asthma, as it indicates that omitting antioxidant-rich foods from the diet, for even a short time frame, will have a detrimental effect on asthma symptoms."

Ironically, the low antioxidant diet consumed by subjects, where they were restricted to one serving of fruit and up to two servings of vegetables per day, is typical of Western diets. In other words, the low antioxidant diet they used to worsen people's asthma, crippling their lung function, was just like the standard American diet.

As about "half the population usually consumes a diet with an intake of fruit and vegetables equivalent to that in the study diet or less, it appears likely that this dietary pattern, which must be considered suboptimal for lung health, may have a significant impact on asthma management, indicating the potential for typical Western dietary patterns to contribute to a worsening of lung function and asthma control."

Within just days, cutting down fruit and vegetable intake can impair lung function, but does adding fruits and vegetables help with asthma? That was the second phase of the study.

Asthmatics on the standard American diet had about a 40% chance of relapsing into an asthma exacerbation within three months. However, put them on seven servings of fruits and vegetables a day instead of three, and we cut their exacerbation rate in half, down to 20%. Imagine if there were a drug that could work as powerfully as a few fruits and vegetables.

If manipulating antioxidant intake by increasing fruit and vegetable intake can so powerfully reduce asthma exacerbation rates, why not just take antioxidant pills instead? I cover that in my video Treating Asthma With Plants vs. Supplements?

Asthma is the most common chronic disease in children and the prevalence is increasing around the world. Despite this, most research dollars are spent on adult chronic disease. "One might ask," a group of researchers posited "whether this is because our politicians and senior administrators feel themselves to be more likely to suffer from the latter, and thus ignore allergic diseases as they mostly impact children and young adults" - who don't vote.

An enormous study about asthma and allergies in childhood, highlighted in my video, Preventing Asthma with Fruits and Vegetables, was published that includes more than a million children in nearly a hundred countries, making it the most comprehensive survey of asthma and allergies ever undertaken. The researchers found striking worldwide variations in the prevalence and severity of asthma, allergies, and eczema--a 20 to 60-fold difference in prevalence of symptoms of asthma, allergic runny nose, and atopic eczema around the world. The large variability suggests a crucial role of local characteristics that are determining the differences in prevalence between one place and another.

What kind of environmental factors? Why does the prevalence of itchy eyes and runny noses range anywhere from 1% in India, for example, and up to 45% of kids elsewhere? There were some associations with regional air pollution and smoking rates, but the most significant associations were with diet. Adolescents showed a consistent pattern of decreases in symptoms of wheeze (current and severe), allergic rhinoconjunctivitis, and atopic eczema with increases in per capita consumption of plant foods. The more their calories and protein came from plant sources, the less allergies they tended to have.

In general, there seems to be an association between an increase in asthma prevalence and a decrease in consumption of fresh fruits, green vegetables, and other dietary sources of antioxidants, helping to explain why the prevalence of asthma and respiratory symptoms are lower in populations with high intake of foods of plant origin. High intakes of fat and sodium, and low intakes of fiber and carbohydrates, are linked with asthma, while traditional and vegetarian diets are associated with lower rates. For example, if we look closer within India, in a study of more than 100,000 people, "those who consumed meat (daily or occasionally) were more likely to report asthma than those who were strictly vegetarian." This also meant avoiding eggs.

Eggs have been associated (along with soft drink consumption) with increased risk of respiratory symptoms and asthma in schoolchildren. On the other hand, consumptions of soy foods and fruits were associated with reduced risk of respiratory symptoms. In fact, removing eggs and dairy from the diet may improve lung function in asthmatic children in as little as eight weeks. Therefore, it may be a combination of eating fewer animal foods and more plants.

High vegetable intake, for example, has been found protective in children, potentially cutting the odds of allergic asthma in half. And fruit has also shown a consistent protective association for current and severe wheeze and runny nose in adolescents, and for current and severe asthma, allergies, and eczema in children.

Why is this? I've talked about the endocrine-disrupting industrial pollutants (see Dietary Sources of Alkylphenol Endocrine Disruptors) building up in the meat supply that may increase the risk of allergic disease, but the increase in asthma may be a combination of both a more toxic environment and a more susceptible population. One review notes that, "The dietary changes which have occurred over recent years may have led to a reduction in these natural antioxidant defenses, resulting in a shift of the antioxidant status of the whole population and leading to increased susceptibility to oxidant attack and airway inflammation."

In adults, for example, the risk of airway hyper-reactivity may increase seven-fold among those with the lowest intake of vitamin C from plant foods, while those with the lowest intake of saturated fats may have a 10-fold protection, presumably because of saturated fat's role in triggering inflammation.

The protective effect of plant-based food may also be mediated through effects on intestinal microflora. It turns out that differences in the indigenous intestinal flora might affect the development and priming of the immune system in early childhood. Kids with allergies, for example, tend to be less likely to harbor lactobacilli, the good bacteria that's found in fermented foods, and naturally on many fruits and vegetables. Lactobacillus probiotics may actually help with childhood asthma, which may help explain why children raised on largely organic vegetarian diets may have a lower prevalence of allergic reactions. Infants raised this way tend to have more good lactobacilli in their guts compared to controls, though they were also more likely to have been born naturally, breastfed longer, and not been given antibiotics, so we can't really tell if it's the diet until we put it to the test (See Treating Asthma with Fruits and Vegetables).

We've known that increased nut consumption has been associated with a reduced risk of major chronic diseases, such as heart disease and diabetes. But do those who eat nuts actually live longer lives? Clinical trials have shown nuts help lower cholesterol and oxidation, and improve our arterial function and blood sugar levels. Does all this translate into greater longevity?

Researchers at Harvard examined the association between nut consumption and subsequent mortality of over 100,000 people followed for decades. In that time, tens of thousands died, but those that ate nuts every day lived significantly longer. Daily nut consumers had fewer deaths from cancer, heart disease, and respiratory disease, even after controlling for other lifestyle factors. Nut consumers lived significantly longer whether they were older or younger, fat or skinny, whether they exercised more, smoked, drank, or ate other foods that may affect mortality.

But nuts are so filled with fat that there "may be a concern that frequent nut consumption can result in weight gain." However, that's not what the Harvard researchers found. In fact, other studies have associated nut consumption with a slimmer waist, less weight gain, and lower risk of obesity. If we look at all the studies put together, it's pretty much a wash. Diets enriched with nuts do not seem to affect body weight, body mass index, or waist circumference much at all. For example, one of the most recent such studies, highlighted in my video, Nuts May Help Prevent Death, in which subjects were told to add either 0, 70, or 120 pistachios to their daily diet as an afternoon snack every day for three months, found no noticeable difference between the three groups. You couldn't see any difference between those eating no nuts and those eating more than 100 a day. Hence, it appears that the incorporation of nuts (around one to two small handfuls a day) would be advisable to ensure various health benefits without the risk of body weight gain.

How nuts do we have to go? Not much. Just a few servings a week may boost our lifespan and lower cancer rates--but it appears we have to keep it up. In the PREDIMED study, when long-time nut eaters were told to cut down on eating nuts or choose extra virgin olive oil, within five years they apparently lost much of their longevity benefit. Only the group that started out eating nuts and continued to eat at least the same amount of nuts died significantly less often.